View source for DoveCot, move messages from certain domains to folder

= Goal =
We will assume the user you are creating filters for is "petra". Petra does not want to see messages from certain domains (corporations) but does want to keep them for a while in her trash, so she can find them if someone calls her and references "his mail from yesterday".

= Possible destination folders =
Get a list of folders
 ls -d /home/petra/Maildir/.*

You will see something like this:
 /home/petra/Maildir/.INBOX
 /home/petra/Maildir/.INBOX.Trash
 /home/petra/Maildir/.INBOX.Archives
 /home/petra/Maildir/.INBOX.Sent
 /home/petra/Maildir/.INBOX.Templates
 /home/petra/Maildir/.INBOX.Junk
 /home/petra/Maildir/.INBOX.Drafts

What you get may differ. If - for example - you use Outlook, chances are your output is completely different. That is NOT important. Important is to  know what DoveCot works with. So, our target folder for this example is "/home/petra/Maildir/.INBOX.Trash".
Inside the filter we will use the "save" command. If given a relative destination, it will insert the home folder of the current user before the given folder. So we will just use "Maildir/.INBOX.Trash/" to be able to copy the file from user to user.

= .forward file =

We create a ".forward" file in the home directory of Petra. Could be something like
 vi /home/petra/.forward

The ownership of the ".forward" file is important. If you just copy the ".forward" file and don't modify the ownership, the ".forward" will not be used.

 chown petra:petra /home/petra/.forward

== filter ==

We want a filter for Domain.bad.1 and Domain.bad.2.
This is the .forward file:
  # Exim filter
  if  $sender_address contains @domain.bad.1 or
      $sender_address contains @domain.bad.2
  then
      save Maildir/.INBOX.Trash/
  endif